Equinox was a long-running Channel 4 popular science and documentary programme. The series ran from 1986 to 2001, originally aired on a weekly basis. The number of films per series fell over the years, from eighteen one-hour films a year originally to twelve by the late 1990s. The last regular series was shown in 2001, with six films. One-off films have occasionally been aired under the title "Equinox Special".